Guys,
I know that everyone is trying to think of ways to get more air (scoops, filters, etc.) I was contemplating the effect that blocking off the hood intake would have... Before I get flamed, wouldn't this actually have a beneficial side? Surely, at speed, there is more than enough air forced in from behind the grille & lower intake. Wouldn't blocking off the cowl duct provide a ram air benefit by not allowing this pressure to escape. I realize there may be some loss at lower speeds and maybe some additional drag. Anybody tried this? Am I thinking beyond reason? Thoughts...

When not at WOT it's like having two windows open in a house and moves more air, but when at WOT it sucks air in. Thought someone attached a string to the vent to see what it does and those were the results?

That hood scoop is a vent 90% of the time, and at WOT, the opening provides extra air volume for the engine intake.

At anything less than WOT, it keeps cool air coming in from the kidney grills and the lower bumper opening. Warm air is allowed to blowing out the vent under low to moderate speeds. (to prevent heat soak)

To the OP: If you actually close off this hood air intake/vent opening, I'm fairly certain that you find that it's a detriment to your performance. The intake system will retain heat (especially in the hotter summer months) that would normally vent off to atmosphere.

The hood intake/vent becomes a negative pressure (vacuum) suction source at WOT, and this additional air intake source supplement the air coming in from the lower bumper area, and the kidney grills. The factory air box/intake system is a very elaborate design, and it's very efficient at gathering a copious amount of fresh air to feed our 4.0 liter V8 engine.

This is why the OEM design is so hard to beat.

All you really NEED, is a high performance drop-in cotton gauze type air filter element to maximize the performance of the factory airbox the BMW engineers have already built for us.

Thanks to all for not roasting me with the button. Obviously I expected there was a reason for the darn thing, but LeMans_Blue_M takes the prize again... I have seen the water spray, and suspected additional benefits at low speed W.O.T. but the heat sink issue escaped me. You guys are the best. High Flow filter it is!